Method and apparatus for making metallic, non-rotationally symmetric rings

ABSTRACT

In a method of making a metallic, non-rotationally symmetric ring with substantially constant wall thickness about its circumference, in particular a cam ring, from a circular ring, a circular ring is mechanically machined on both inner and outer sides with an edge-shortening form element and then intermittently fed by a transport belt to an area between two continuously closing and opening die members. The transport belt is hereby positioned with its upper strand below the die members. After closing the die members, the circular ring is shaped through cold forming to a non-rotationally symmetric shape whereby the die members continue to maintain the closed position momentarily before being opened for removal of the non-rotationally symmetric ring from the area between the die members.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No. 103 32 069.5, filed Jul. 8, 2003, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates, in general, to a method and apparatus for making metallic, non-rotationally symmetric rings.

German Pat. No. DE 101 34 776 A1 describes a method for making metallic, non-rotationally symmetric rings with a constant wall thickness about their circumference. Hereby, circular ring blanks of equal width are severed from a hot-rolled pipe and mechanically machined on all sides. The non-rotationally symmetric shape is produced by cold forming carried out in a forming tool having two die members and configured with an inner contour which approximates the final contour of the non-rotationally symmetric ring.

It would be desirable and advantageous to provide an improved method and apparatus for making metallic, non-rotationally symmetric rings to obviate prior art shortcomings and to provide a cold-forming operation which is easy to implement and carried out at a high cycle rate.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a method of making a metallic, non-rotationally symmetric ring with substantially constant wall thickness about its circumference, in particular a cam ring, includes the steps of mechanically machining both sides of a circular ring to provide on the inside and outside edge-shortening form elements, feeding the circular ring incrementally to an area between two continuously closing and opening die members, closing the die members for cold forming the circular ring into the shape of a non-rotationally symmetric ring, maintaining the die members in closed position for an additional short time, and opening the die members for removal of the non-rotationally symmetric ring from the area between the die members.

The present invention resolves prior art problems by providing the circular ring during preceding mechanically machining of the circular ring, on the inside and outside with edge-shortening forming elements, such as radii and/or bevels, and continuing to hold the shaped ring for a short time between the closed die members before being ejected. This mode of operation results in a simple method that can be carried out at a high cycle rate. As is generally known, metallic bodies that are subjected to a cold forming process exhibit a tendency to swell elastically after the forming tool is opened. By maintaining the die members in closed position for a short time longer, any shift in the crystal structure during cold forming is able to “settle” so that the previously encountered swelling effect is neutralized and the finished contour of the non-rotationally symmetric ring can be produced within narrow tolerances.

According to another feature of the present invention, the circular ring may be cold formed in horizontal disposition. This facilitates feeding of the circular ring, on the one hand, and positioning of the circular ring during cold forming, on the other hand.

According to another feature of the present invention, at least the inner contour surface of each of the die members is continuously lubricated. In this way, friction between the inner contour surfaces of the die members and the narrow outer surface area of the circular ring is decreased.

According to another aspect of the present invention, an apparatus for making a metallic, non-rotationally symmetric ring with substantially constant wall thickness about its circumference, in particular a cam ring, from a circular ring, includes a frame bed, a forming tool supported by the frame bed and having an inner contour which approximates a finished contour of a non-rotationally symmetric ring, wherein the forming tool includes two die members constructed in the form of two flat disks in opposite disposition and movable back and forth, and an endless transport belt arranged in an area between the die members and so operated as to move in a production clock cycle and to move transversely to the die members, with the transport belt having an upper strand extending in immediate proximity underneath the die members.

In order to prevent damage to the transport belt as the die members oscillate, the upper strand of the transport belt has a top side which is spaced from the underside of the die members at a distance which is at least 0.05 mm. The following fact is hereby exploited: Cold forming of the circular ring leads in the region of greatest deformation, which is generally the region of greatest deviation from the original circular shape, to minor material accumulation in the respective edge zone of both end surfaces. To minimize this effect, the circular ring is provided during the preceding mechanical machining process on both sides, on the inside and the outside, with edge-shortening form elements, such as radii and/or bevels. The extent of edge shortening depends hereby on the size of the cross sectional area and can amount to one millimeter. The provided form elements on the outside are used to produce the required distance between die members and transport belt such that the die members engage the outer surface area of the circular ring on the transport belt, whereby the engagement begins only by the distance of the edge shortening from the disposition of the circular ring on the transport belt. As a consequence, a direct contact with the die members is not required for the shaping process during cold forming in the edge area of the mechanically machined ring.

According to another feature of the present invention, the transport belt may be provided in midsection with vertical engagement pins, which are spaced apart in length direction of the transport belt, for supply of the circular rings. Typically, the forming tool is preceded by an apparatus for singling circular rings before supply to the forming tool. The singling apparatus normally includes hereby an open-topped drum which rotates slowly and is provided on the inside with a screw and a deflector. At the singling position, the circular ring slides onto the transport belt via a cage having an outlet above the respective engagement pin. Stopper pins moving cyclically make sure that only a single ring is positioned at the end of the cage outlet for subsequent timed placement of the ring on the transport belt upon the engagement pin in surrounding relationship thereto. The incremental movement of the transport belt results in a supply of the circular ring to the forming tool. After conclusion of the cold forming process and opening of the die members, the engagement pin engages the non-rotationally symmetric ring and ejects the ring in the area of the belt-reversing roller from the transport belt.

According to another feature of the present invention, the die members have end surfaces in confronting relationship, with each end surface provided with two centering elements. In this way, it is ensured that the die members are precisely positioned in relation to one another. Suitably, the centering elements of one die member may be configured with a triangular pointed end, and the centering elements of the other die member may be configured with a complementary recess. The legs of the pointed ends and the legs of the recesses assume hereby the centering function.

According to another feature of the present invention, a press may be arranged downstream of the forming tool and have an upper die and a lower die. Through provision of the press, the presence of material accumulations, as described above, can be further decreased. The non-rotationally symmetric ring can hereby be placed flatly between the dies and then compressed. Suitably, the forming tool and the press may be integrated in a common shaping unit. As an alternative to the provision of a press for minimizing the presence of material accumulations, it is, of course, also conceivable to simply grind away the material accumulations, partially or entirely, after conclusion of the final heat treatment of the rings.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

FIG. 1 is a longitudinal section of an apparatus for making metallic, non-rotationally symmetric rings in accordance with the present invention;

FIG. 2 is a plan view of the apparatus of FIG. 1;

FIG. 3 is a sectional view, on an enlarged scale, of the apparatus, taken along the line III-III in FIG. 2;

FIG. 4 is a detailed view, on an enlarged scale, of an area marked X in FIG. 3; depicting the die members in open position;

FIG. 5 is a sectional view of the area X, depicting the die members in closed position; and

FIG. 6 is a front view of a produced cam ring.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

Turning now to the drawing, and in particular to FIG. 1, there is shown a longitudinal section of an apparatus for making metallic, non-rotationally symmetric rings in accordance with the present invention. The apparatus includes a forming tool, generally designated by reference numeral 20 and having an inner contour which approximates a finished contour of a non-rotationally symmetric ring to be made. As shown in FIG. 2, which is a plan view of the apparatus, the forming tool 20 has a frame bed (not shown) and two die members 1, 2 which are supported by the frame bed and move cyclically to and fro, as indicated by double arrow 3. It will be appreciated by persons skilled in the art that the forming tool 20 must contain much mechanical apparatus which does not appear in the foregoing Figures, e.g. a drive for moving the die members. However, this apparatus, like much other necessary apparatus, is not part of the invention, and has been omitted from the Figures for the sake of simplicity.

Disposed below the forming tool 20 and moving transversely to the die members 1, 2 is an endless transport belt 4 which is looped about belt-reversing rollers 5, 6 at the end zones of the transport belt 4 and moves in a direction indicated by arrow 10. On its topside, the transport belt 4 is provided approximately in midsection thereof with a plurality of engagement pins 7 which are spaced apart in length direction of the transport belt 4.

Arranged at the right hand side of FIG. 1 is a feed unit 8, shown only schematically, to place single ring blanks 9 on the transport belt 4. The ring blanks 9 are mechanically machined on all sides and have a circular configuration.

Shaping of the ring blanks 9 through a cold forming process in the forming tool 20 to produce, for example, a cam ring 11, as shown in FIG. 6, is as follows: The ring blanks 9 are delivered intermittently by the feed unit 8 to the transport belt 4 in such a manner that an engagement pin 7 enters the opening of the ring blank 9 at the singling position at the end of the feed unit 8 to advance the ring blank 9. As the transport belt 4 advances, the respective ring blank 9 is moved by the engagement pin 7 into the area between the die members 1, 2 which move cyclically to and fro between open and closed positions.

FIG. 2 shows the disposition of a ring blank 9 upstream of the forming tool 20 and the disposition of a ring blank 9 in the area between the open die members 1, 2 of the forming tool 20. At this point, die members 1, 2 close and shape the circular ring blank 9 into the non-rotationally symmetric cam ring 11 through cold forming. Before the die members 1, 2 open again, the shaped cam ring 11 is held in the constrained position, as the closed position of the die members 1, 2 is maintained for a short time longer, to thereby control elastic swelling.

After opening the die members 1, 2, the cam ring 11 is advanced incrementally by the transport belt 4 until being dropped into a container 12 at the end of the transport belt 4.

Turning now to FIGS. 3, 4 and 5, there are shown details of the apparatus to illustrate the absence of a contact between the advancing transport belt 4 and the oscillating die members 1, 2. As the ring blank 9 to be shaped rests flatly on the top surface of the transport belt 4, the underside of the oscillating die members 1, 2 moves at a distance 13 to the topside of the upper strand of the transport belt 4 above the transport belt 4. The distance of the upper strand of the transport belt 4 to the underside of the die members 1, 2 is at least 0.05 mm. This requires, as shown in FIG. 5, that the ring blank 9 is provided on both sides, on the inside and the outside, with edge-shortening form elements 14, such as radii and/or bevels. As a consequence, the die members 1, 2 bear only against the outer surface area of the ring blank 9, and the required distance 13 between the top surface of the transport belt 4 and the underside of the die members 2 is maintained. In other words, the form elements 14 are provided in the edge areas most likely to experience material accumulation during the cold forming process so that material can be displaced into the free space as a result of the form elements 14 and is prevented from migrating into the area between the die members 1,2 and the transport belt 4. The extent of edge shortening depends hereby on the size of the cross sectional area and can amount to one millimeter.

The cam ring 11, produced in this way, is shown in FIG. 6, with those regions that may encounter material accumulation being marked by reference numeral 15. Material accumulation may occur in particular in those regions that undergo the greatest deformation from round to substantially straight. The extent of possible material accumulation is dependent on the flow behavior of the material, on the degree of deformation, and on the material thickness. The present of material accumulation can be minimized through subsequent cold pressing between two flat dies of a press or may be eliminated altogether by mechanical machining, such as grinding. When providing a press, the press and the shaping tool are integrated in a common shaping unit.

Although not shown in detail in the drawing, the die members 1, 2 are provided at their confronting end surfaces with a complementary centering mechanism. An example of such a centering mechanism includes the provision of two centering pin extending out from the end surface of one of the die members 1, 2 for engagement in complementary recesses in the end surface of the other one of the die members 1, 2. Suitably, the centering pins have a triangular pointed end for engagement in the complementarily configured recesses.

While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: 

1. A method of making a metallic, non-rotationally symmetric ring with substantially constant wall thickness about its circumference, in particular a cam ring, comprising the steps of: mechanically machining both sides of a circular ring to provide on the inside and outside edge-shortening form elements; feeding the circular ring incrementally to an area between two continuously closing and opening die members; closing the die members for cold forming the circular ring into the shape of a non-rotationally symmetric ring; maintaining the die members in closed position for an additional short time; and opening the die members for removal of the non-rotationally symmetric ring from the area between the die members.
 2. The method of claim 1, wherein the circular ring is cold-formed in horizontal disposition.
 3. The method of claim 1, and further comprising the step of continuously lubricating an inner contour surface of each of the die members.
 4. The method of claim 1, wherein the edge-shortening form element is a radius.
 5. The method of claim 1, wherein the edge-shortening form element is a bevel.
 6. Apparatus for making a metallic, non-rotationally symmetric ring with substantially constant wall thickness about its circumference, in particular a cam ring, from a circular ring, comprising: a frame bed; a forming tool supported by the frame bed and having an inner contour which approximates a finished contour of a non-rotationally symmetric ring, said forming tool including two die members constructed in the form of two flat disks in opposite disposition and movable back and forth; an endless transport belt arranged in an area between the die members and so operated as to move in a production clock cycle and to move transversely to the die members, said transport belt having an upper strand extending in immediate proximity underneath the die members.
 7. The apparatus of claim 6, wherein the upper strand has a top side spaced from an underside of the die members at a distance which is at least 0.05 mm.
 8. The apparatus of claim 6, and further comprising a machining device for shortening an inside edge and an outside edge of a circular blank before the circular ring is placed between the die members for shaping the circular blank into the non-rotationally symmetric ring.
 9. The apparatus of claim 8, wherein the machining device is constructed to radius the inside and the outside edges.
 10. The apparatus of claim 8, wherein the machining device is constructed to bevel the inside and the outside edges.
 11. The apparatus of claim 8, wherein the inside and the outside edges are shortened by up to one millimeter.
 12. The apparatus of claim 6, wherein the transport belt is provided in midsection with vertical engagement pins which are spaced apart in length direction of the transport belt.
 13. The apparatus of claim 6, wherein the die members have end surfaces in confronting relationship, each said end surface provided with two centering elements.
 14. The apparatus of claim 13, wherein the centering elements of one die member are configured with a triangular pointed end, and the centering elements of the other die member are configured with a complementary recess.
 15. The apparatus of claim 6, and further comprising a press arranged downstream of the forming tool and having an upper die and a lower die.
 16. The apparatus of claim 15, wherein the forming tool and the press are integrated in a common shaping unit. 